ANALYSIS OF VEGETATION SENSITIVITY TO CLIMATE VARIABILITY OVER BORNO STATE, NIGERIA.

Abstract

This study aims at assessing the effect of variability of climatic parameters (precipitation and temperature) on vegetation condition in Borno State. Gridded rainfall and temperature data was acquired from ERA-Interim website. Precipitation and temperature data for ground stations was acquired from Nigerian Meteorological Agency (NiMet). Landsat Thematic Mapper (TM), Enhanced Thematic Mapper (ETM) and Operational Land Imager (OLI) imageries covering the study area (Borno State) was acquired from United States Geological Survey (USGS) website. Trend analysis was used to plot the pattern of rainfall and temperature on monthly, annually and decades’ bases. Standard Precipitation Index (SPI) was used to identify wet and dry years. Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) was used to monitor the vegetation health condition and vegetation moisture content in Borno State respectively. Vegetation Condition Index (VCI) was used to classify the drought as it affects vegetation in Borno State. The trend shows that there were nine peak years of rainfall in the 3 decades with the month of August having the highest rainfall amount throughout the 3 decades, with average values of 5.4mm for 1984 – 1993 (first decade), 6.4mm for 1994 – 2003 (second decade) and 7.2mm for 2004 – 2013 (third decade). Also in all the years, April and May were found to have the highest temperature and January has the lowest. The Standard Precipitation Index (SPI) indicated five (5) dry years during the study period with year 1984 as the driest year and 1985, 1987, 1990 and 1994 as moderately dry years. Comparison of NiMet and Gridded rainfall and temperature values with NDVI shows that NiMet rainfall and temperature data has a better relationship with NDVI. Gridded and NiMet rainfall and temperature data has strong relationship with NDWI. This indicates that temperature and rainfall has significant impact on vegetation health and moisture content in Borno State. The Vegetation Condition Index (VCI) shows that five (5) vii years were affected by drought effect with year 2000 having large areas covered by moderate drought. The changes in vegetation condition as a result of climate variability serves as a basis for initiating a discussion on the types of measures to be adopted to attenuate the effects of global climate change.